In programming a non-volatile memory cell, a programming pulse is applied on the wordline of the memory cell, and the bitline of the memory cell is driven to ground. After a period of time, the memory cell is placed in a programmed state. In some programming methods, the duration of the programming pulse is made relatively long to ensure that the memory cell will be programmed. Because the duration of the programming pulse is often set for worst-case conditions, this xe2x80x9cover-provisioningxe2x80x9d approach can result in excessive average programming time, power, and energy. Additional delays are introduced because memory cells are programmed on a wordline-to-wordline basis. Specifically, the duration of the programming pulse applied to a wordline is the same regardless of the number of memory cells that are to be programmed. For example, if the duration of the programming pulse is 10 microseconds per memory cell and there are 1024 memory cells along a wordline, a programming pulse is applied to the wordline for 10,240 microseconds even if only one memory cell is to be programmed. If the first memory cell is to be programmed, its bitline is driven to ground during the first 10 microseconds that the programming pulse is applied to the wordline; otherwise, the bitline is kept high. After the first 10 microseconds have passed, the second memory cell can be programmed by driving its bitline to ground. This process continues until the last memory cell along the wordline is given an opportunity to be programmed.
There is a need, therefore, for a method and system for increasing programming bandwidth in a non-volatile memory device.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims.
By way of introduction, the preferred embodiments described below provide a method and system for increasing programming bandwidth in a non-volatile memory device. In one preferred embodiment, a memory device is provided with a plurality of bits to be stored in a respective plurality of memory cells along a wordline. Some of the bits represent a programmed state, and others represent an un-programmed state. The duration of the programming pulse applied to the wordline is determined by the number of bits that represent the programmed state. In another preferred embodiment, the plurality of bits to be stored in the memory device comprises a first set of bits representing a modification to the stored data and a second set of bits representing an un-programmed state. Other preferred embodiments are provided, and each of the preferred embodiments can be used alone or in combination with one another.
The preferred embodiments will now be described with reference to the attached drawings.